碘(V)-碘化物-番红花红T体系双波长分光光度法测定食盐中碘

Double-wavelength spectrophotometric determination of iodine in saltwith I(V)-iodide-safranine T system

在0．2mol／L磷酸中，碘（V）与过量的I-反应生成I3-，I3-进一步与番红花红T（ST）形成稳定的2：1离子缔合物，360nm处出现正吸收峰，513nm处出现负吸收峰。选定测量波长为360nm，参比波长为513nm，建立了双波长分光光度法测定碘的新方法。碘（V）浓度在0～0．7μg／mL范围内服从比尔定律，表观摩尔吸光系数为1．27×10^5L·mol^-1·cm^-1，检出限为11．9μg／L。方法用于测定低钠盐和锌强化营养盐中碘，结果与碘量法一致，相对标准偏差小于1．54％（n=5），回收率为98．4％～99．1％。

A new method for determination of iodine was developed by double-wavelength speetrophotometry u- sing 360 nm as the measurement wavelength and 513 nm as the reference wavelength. The method is based on the reaction of I（V） with excess I in 0.2 mol/L H3PO4 to produce I3 ,and it further reacts with safranine T （ST） to form a stable ion-association complex（2 ： 1）, which exhibiting a positive ab- sorption peak at 360 nm and a negative absorption peak at 513 nm. Beer＇s law was obeyed for 0 0. 7 μg/mL I（V）. The apparent molar absorptivity was 1.27 × 10^5 L · mol^-1 · cm^-1 , and the limit of detection was 11.9μg/L. The method was applied to determine iodine in low sodium salt and salt for- tified with zinc. The results showed good agreement with those obtained by iodimetry. RSD was less than 1.54 %（n = 5）. Recovery varied from 98.4 % to 99.1%.